In motor vehicles, with automated transmissions or automatic transmissions with an automated friction transmission as the starting drive element, several sensor data, relevant for operation, are provided to an electronic control unit, positioned between the engine and the transmission for controlling the torque transfer, such as engine rotation speed, transmission input rotation speed, drive pedal position, speed, and shift intention and, after the appropriate analysis, the engagement or the disengagement of the clutch is initiated, if necessary, having a variable level of engagement or level of disengagement.
It is known in the art to verify the individual way point conditions during the movement of the friction parts of the clutch, through learning of characteristic way points of the clutch, for achieving a perfect and comfortable start operating and shift conditions and for permanently maintaining them. As a rule, this is achieved through cyclic engagement or disengagement motions of the clutch whereby, in each case, the relevant parameters are considered, such as the idle rotation speed of the engine, being linked with the primary side of the clutch, and the transmission input rotation speed at the secondary side of the clutch, being linked with the transmission input shaft, and the way gradient when engaging the clutch. Through their pattern or course, respectively, distinct clutch way points are detected, and can be learned into or being learned, respectively.
For example, DE 103 52 611 A1 recommends a method of adoption of a clutch way point, when engaging and at the beginning of friction, through which the learning of this way point is achieved at clutch disengagement, by capturing of a difference in rotation speed between the clutch input and output side. In addition, when engaging the clutch, a second way point can be established by considering a hysteresis of the clutch way points.
In DE 100 54 867 A1, a method is presented for adopting a clutch way point, determined as a creeping point for adjusting a desired creeping torque. Hereby, the actually transmitted torque is compared to a previously configured creeping point cycle and, in case of a deviation, is adopted by a desired creeping torque when starting and engaging a gear, between a friction way point and the creeping point, defined as an assumed reference point, generating a new creeping point which corresponds with the desired creeping torque.
The EP 0 725 225 B1 describes a method for establishing a clutch way point, defined as a point of contact, in which the clutch is moving at a constant velocity, in the direction of engagement, and is engaged by capturing the rotation speed difference of a transmission shaft over time, at two positions of the engaging way points and a point of contact, ahead of the first position, is assumed.
In addition, other methods are known in the art which are not dependent on engine related sensor data or transmission input rotation speed data.
The DE 101 63 438 A1 proposes such a method for establishing a clutch application point, which is determined as a limit value in case of further engagement of the clutch and the resulting torque transfer. Here, one control parameter is varied. Particularly, the point of engagement is recognized, due to an unsteady gradient pattern of a disengagement force or due to an engagement force of the clutch which is approaching a ZERO value. The method is also applicable when the engine is being turned off.
In DE 103 06 934 A1, another method for determining the point of engagement and a beginning torque transfer is revealed, without including engine related sensor data, in which an unsynchronized reverse gear position is used. Hereby, a presently stationary vehicle with an idling engine, a point of engagement is set, when the torque transfer is sufficient enough, when being in a tooth-on-tooth position, to sliding the teeth of a sliding sleeve against a clutch body of a reverse gear wheel.
The methods in the above mentioned examples, as well as additional approaches known to those skilled in the art, for determining other needed clutch way points, especially the engaged position, meaning the fully engaged clutch position, the engagement of the clutch not having any way changes anymore, and a secure disengagement of the clutch by considering a constructional related clutch stroke, result in a clutch travel and coordinate system, or to a coordinate axis, respectively, through which certain function of the clutch can be realized, i.e., the clutch function “disengage clutch during shifting”, or the clutch function “wait position when the vehicle is stationary, with a gear position selected, until starting is signaled”.
It needs to be considered, when operating the clutch, that the way point settings and, therefore, also the torque transfer of the clutch might be changing over its life expectancy, especially because of wear, as well as during the actual operating and external influence, for instance varying temperature and varying rotation speed. Therefore, the learning process of the mentioned clutches is usually accomplished during each clutch stroke, or at least during each starting operation, to match the relevant clutch way points with the actual way point conditions or to adopt them, respectively. In addition, after each learning process, when the transmission is shifted to a neutral position and the engine is idling, the clutch is generally engaged and disengaged when the driver selects a starting gear position.
The known clutch control has the disadvantage in learning the clutch positions, based on the previously described function sequence, that the required time for it is relatively long and that the driver's intent for fast starting and shifting might be unnecessarily and possibly delayed.